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Question: Distributor Noise I think.

Marv02

Well-known member
Joined
May 4, 2010
Messages
472
Location
California City Ca
Corvette
1986 C-4 Corvette
I been trying to find a tapping sound the motor has about 7000 miles on it CC Ultra Magnum pro Steel full roller arms.
The rocker arms do make some noise but this not where the noise is coming from.
I replaced the roller lifters with GM LS7 lifters, Put new push rods in it just in case checked push rod lengths there good and as long I had it apart.
Tried many times to readjusting the valves preload.
The distributor has a Composite gear on it for the Roller cam.
Used the screwdriver to ear trying to find where the noise is coming from just can’t find it you can hear well thought the rear of the plenum area.
At first I was thinking it was a intake valve slamming close but they say the LT4-hotcam should not make this noise because you can hear it in the rear plenum area.
I was thinking it could be a bad bearing in the Distributor it’s pretty loud during cold start up after warms up it is still there but not bad but it is still there.
Just makes me nervous knowing it is not right it has made this noise from day one when fired up this motor.
I don’t have a spare Distributor to find out this is it I want to buy a new distributor but if I have to fork out the money might as well buy a nice one MSD Malory DUI which one to buy the car rev to 5500 RPM’s it is a street car.
I would like the smaller distributor cap makes things easier to get to and work on would be a big plus.
 
I am using Lunati valve spring part #73943.
With LT4 Hotcam do you think this could be where my noise is comming from.
Here are the spec's
Lunati 73943 - Lunati Valve Springs Details
Valve Spring Sets
Description Single Spring
OD 1.266''
ID .883''
Installed Height 1.750''
Installed Pressure 108
Open Height 1.250''
Open Pressure 339
Coil Bind 1.060''
Max Lift 0.630''
Spring Rate 462


Now OEM Hotcam Spring Spec's
LT4 Valve Spring Specifications
Part Number 12551483
Material Chrome Silicon SuperClean
Outside Diameter 1.337”
Inside Diameter 0.906”
Installed Height 1.780”
Seat Load 101 lbs.
Average Spring Rate 331 lbs./inch
Solid Height 1.215”
 
why would it only be in one area and not all of the valve-train?
IMO it seems more likely to be related to the dist drive, oil pump drive or even camshaft end runout....a careful timing of the noise helps tell you what its related to.

Time it and see if its the same speed of the cam or the crank....that helps to pin it down.I've been told that flywheel bolts can cause this, loose TC, crank runout, just about everything on the end of the crankshaft.

For now I'd pull the dist and look carefully at the drive gear teeth and find a scratch or some defect on a tooth. Look for the wear pattern on each tooth and make sure its the same on all. I've seen a slight ding in a tooth cause a knock noise that sounded like a rod bearing. It don;t take much.
 
Okay this very Weird one the Noise is comming from the fuel regalator.
WTF thats what I was thinking.
 
I pull the fuel regalator apart I made it adjusable long time ago I removed the adjustment screw and washer that I think was making the noise welded up the bolt hole for the adjuster put it back together much bettter theres some noise still but much better than before.
 
Just Ordered a fuel pressure regulator pulse dampener.
I been chasing this noise for almost a year now.:happyanim:
 
Yeah, I know the feeling...

I thought I had an exhaust leak at a header gasket...kept hearing that spitting, clicking sounds when I stepped in it.

After making myself crazy tightening, looking at and going thru the gaskets and donuts...it turned out to be a sticky A.I.R. check valve that was letting exhaust blow backward into the air tubes......
 
I had one like that with my F250 4X4 it end up beening a spark plug The way I founfd this when it blew out HaHa lucky it was still under warranty.:chuckle


Yeah, I know the feeling...

I thought I had an exhaust leak at a header gasket...kept hearing that spitting, clicking sounds when I stepped in it.

After making myself crazy tightening, looking at and going thru the gaskets and donuts...it turned out to be a sticky A.I.R. check valve that was letting exhaust blow backward into the air tubes......
 

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